This invention relates to storage systems, and in particular to providing assured levels of quality of service for data protection in such systems.
Large organizations throughout the world now are involved in millions of transactions which include enormous amounts of text, video, graphical and audio information which is categorized, stored, accessed and transferred every day. The volume of such information continues to grow. One technique for managing such massive amounts of information is the use of storage systems. Conventional storage systems can include large numbers of disk drives operating under various control mechanisms to record, mirror, remotely back up, and reproduce this data. This rapidly growing amount of data requires most companies to manage the data carefully with their information technology systems.
One common occurrence in management of such data is the need to provide copies of data as protection in case of failure of the storage system. Copies of the data are sometimes made within the storage system itself, in an operation conventionally referred to as “mirroring.” This can provide reliability in case of component failures. Copies of the data are also frequently made and stored in remote locations by using remote copy operations. The storage of this data in a remote location provides protection of the data in the event of failures in the primary storage system, or natural disasters occurring in the location of the primary storage system. In such circumstances, the data from the remote copy operation can be retrieved from the secondary storage system and replicated for use by the organization, thereby preventing data loss.
Users have many different kinds of data, and the value of the data to the organization is different as well. It would be desirable to have the level of Quality of Service (QoS) for the data protection to be different depending upon the value of the data to reduce the total cost of operations. In such systems, one measure of the QoS level is known as the Recovery Point Objective (RPO). The RPO generally specifies a range of data loss, for example, with high value data associated with minimum data loss and low value data being tolerant of greater loss.
One technique for providing remote copy operations in a storage system is described in commonly assigned “Data Processing System Including Storage Systems,” U.S. application Ser. No. 10/603,076, filed Jun. 23, 2003. Another commonly owned U.S. application Ser. No. 10/022,306, filed Jun. 19, 2003, entitled: “Remote Storage System and Method” describes a system in which data with the highest priority is always copied to the remote site based on that priority.
U.S. Pat. No. 6,487,562 describes a remote copy operation in which a formula of delay time for data with different priority to be copied is employed. The system described there provides copying based upon each track of particular volumes, not based on journal information. In this invention, the remote copy is based upon the copy rate and the journal data, not based upon delay time, tracks or volumes.
One issue which arises in such systems is that the storage system can copy data based on a priority to the remote site. Data with high priority can be copied to the remote site more quickly, and data with lower priority copied later. As a result, data with a lower priority may not be copied to the remote site for a long time depending upon the quantity of data and the bandwidth available. Thus, in some circumstances, depending upon the bandwidth of the copy operation and the extent of high value data, the lower priority data may not be copied to the remote location. What is needed is a system for enabling copying of the data from a primary storage location to a remote location using different levels of priority or different quality of service.